Chapter 25 Populations and Ecosystems
Plants in Relationship to Their Habitats
Biotic Components of the Habitat
habitat = set of conditions for life
Abiotic Components of the Habitat
The Structure of Populations
operational habitat = what affects the plant
population = individuals of same species
community = all populations
ecosystem = all living and nonliving environment #
Soil Factors
Latitude and Altitude #
Climate
abiotic = nonliving
extremes are more important than average
moisture
critically important
growing seasons
tolerance range = between low and high extremes
formed from break down of rock
three horizons
pioneers = first plants in new soil
B Horizon = middle layer; zone of deposition
C horizon = lowest layer; rock
A Horizon = uppermost; zone of leaching
altitude
latitude
day length
sun exposure
seasonal variation
drought
high winds
ozone coverage
poor soil
Disturbance
destroys plants
man made or natural
ex: flood, fire, avalanche
Other Plant Species
Organisms Other Than Plants
The Plant Itself
competition = disadvantageous
competitive exclusion = less adapted plant excluded
mutualism = beneficial for both organisms
niche = particular set of conditions
ecotypes = before subspecies
transplant experiments = do ecotypes exist?
common garden = seeds both sites
biotic = living
predation = one benefits, one harmed
herbivore = eat plants
commensal = one benefitted, one unaffected
pathogenic = fungi / bacteria
browsing = twigs and leaves
herbs
Geographic Distribution
Boundaries of the Geographic Range #
factor exs: rain, warmth, soil, etc.
limiting factor = factor that determines health of plant
Local geographic Distribution
clumped distributions = space between plants is large or small
uniform distributions = evenly spaced
random distribution = no pattern to position
allochemics = chemical inhibits others
allelopathy = inhibition by chemicals
Age Distribution: Demography
age distribution = demography
generation time = birth of individual to birth of it's offspring
intrinsic rate of natural increase = biotic potential
biotic potential = number of viable offspring #
carrying capacity = individuals that the ecosystem can support
r- and K- Selection
K- selection
r-selection
caused by disturbance
some disturbances are predictable - some are not
r selected species = annuals or shrubby perennials
intense competition
can occur next to r - selected
K-selected species = pines and firs
The Structure of Ecosystems
Temporal Structure
SpeciesCompositon
Physiognomic Structure
Trophic Levels
distribution
life forms = classification
physical size and shape
changes during seasons are major
gradual or extreme changes occur in ecosystems
changes in an ecosystem in a period of time #
type of ecosystem
niches
number and diversity of species
primary consumers = energy and nutrient supply
secondary consumers = carnivores
primary producers = autotrophs
decomposers
carbon flow = energy flow - movement through the trophic levels
